Fix Lack of Resources & Rate Limiting in Axum
Unbounded endpoints are a silent killer in high-performance Rust services. In Axum, failing to enforce rate limits or request size constraints allows an attacker to saturate the Tokio runtime or exhaust system memory via heap allocation spikes. Without these guards, your service is a sitting duck for trivial DoS attacks and resource exhaustion.
The Vulnerable Pattern
use axum::{routing::post, Router};// VULNERABLE: No limit on request body size or request frequency. // An attacker can send a multi-gigabyte string to crash the node // or spam this endpoint to exhaust the connection pool. async fn process_data(body: String) -> &‘static str { “Data processed” }
pub fn app() -> Router { Router::new().route(“/api/ingest”, post(process_data)) }
The Secure Implementation
The secure implementation utilizes Tower middleware to enforce strict boundaries. `RequestBodyLimitLayer` acts as a circuit breaker for memory, rejecting any payload exceeding 1MB before it is even parsed into a String. The `RateLimitLayer` throttles the throughput to 5 requests per second; combined with `HandleErrorLayer`, it ensures the application gracefully returns an HTTP 429 status instead of choking under load. For production-grade multi-tenant apps, consider using `tower-governor` for sophisticated IP-based rate limiting.
use ax_um::{routing::post, Router, error_handling::HandleErrorLayer, http::StatusCode, BoxError}; use tower::{ServiceBuilder, limit::RateLimitLayer}; use tower_http::limit::RequestBodyLimitLayer; use std::time::Duration;async fn process_data(body: String) -> &‘static str { “Data processed” }
pub fn app() -> Router { Router::new() .route(“/api/ingest”, post(process_data)) .layer( ServiceBuilder::new() // 1. Handle errors from the middleware (e.g., 429 Too Many Requests) .layer(HandleErrorLayer::new(|err: BoxError| async move { (StatusCode::TOO_MANY_REQUESTS, “Rate limit exceeded”) })) // 2. Rate Limit: 5 requests per 1 second per worker .layer(RateLimitLayer::new(5, Duration::from_secs(1))) // 3. Resource Limit: Max 1MB body size to prevent OOM .layer(RequestBodyLimitLayer::new(1024 * 1024)) ) }
Your Axum API
might be exposed to Lack of Resources & Rate Limiting
74% of Axum apps fail this check. Hackers use automated scanners to find this specific flaw. Check your codebase before they do.
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